1. Technical Field
The present invention embodiments pertain to network formation in wireless networks. In particular, the present invention embodiments pertain to enhancing network formation in wireless networks based on control of network organizational packet transmissions.
2. Discussion of Related Art
Various commercial network formation protocols may be utilized for network formation within a wireless Mobile Ad-Hoc network (MANETs). In particular, a packet transmitted by a node within a wireless mobile Ad-Hoc network is received by all network nodes within RF range of the transmitting node. One of the objectives of these protocols is to minimize the total number of forward transmissions for broadcasting. Flooding is a simple approach, where each network node that receives a packet re-transmits that packet exactly once. Although the flooding technique ensures coverage, the technique is inefficient and causes broadcast storm problems. Two common routing protocols include Ad-Hoc On-Demand Distance Vector (AODV), and Optimized Link State Routing (OLSR). The AODV routing protocol is a reactive protocol that intends to alleviate the overhead problem associated with numerous packet transmissions, and utilizes HELLO packets or messages to determine node connectivity. During a route discovery phase, network nodes exchange periodic HELLO messages with their neighbors in order to establish a list of neighbors at each node. The HELLO packet includes the transmitting node address, a list of neighbors, and the status of links to the neighbors. By way of example, the neighborhood of a node A refers to all nodes that are linked to node A. The links may be symmetric or asymmetric.
The Optimized Link State Routing (OLSR) protocol employs a concept referred to as a two-hop neighbor. For example, a node C is considered to be a two-hop neighbor of node A, if a node B is a symmetric neighbor of node A, and node C is a symmetric neighbor of node B, but node C is not a neighbor of node A. The HELLO packets are utilized by the nodes to generate the immediate and two-hop neighbors, and to determine the quality of the communication links in the neighborhood. This information is stored for a limited time in each node, and needs to be refreshed periodically.
In a route maintenance phase, each network node surveys the link status to neighboring nodes. The HELLO packets are used to maintain connectivity between neighboring nodes, where a link is assumed to be disabled when no HELLO packet is received within a specified time interval. Several network protocols have been proposed to alleviate the overhead problem associated with the numerous packet transmissions of flooding. The OLSR protocol uses a multipoint relay (MPR) mechanism, where each network node uses the two-hop neighbor information to select a minimal set of multipoint relays (MPRs) to enable all nodes within a two-hop neighbor area to be reachable. The MPR flooding mechanism is also used to broadcast topology information throughout the network. Each network node with one or more associated multipoint relays (e.g., a non-empty MPR selector set) periodically transmits a topology control message including the address of the source node and the node multipoint relays (MPRs), thereby announcing node connectivity to node MPRs. Since each node has associated MPRs (e.g., an MPR selector set), the connectivity to all network nodes is announced, and each node receives a partial topology graph of the entire network. The shortest path algorithm is subsequently applied to this partial graph to calculate optimal routes to all nodes. The topology information is maintained for a specified time interval, and needs to be refreshed periodically.
However, the neighbor discovery and network formation aspects of the commercial protocols for Mobile Ad-Hoc networks (MANETs) described above are not suitable for tactical or other types of applications. For example, these types of applications or networks require severe timing constraints and security features. Further, the neighbor discovery protocols described above may need to adapt to asymmetrical links, and the HELLO packets are rather large, thereby significantly increasing bandwidth overhead. In addition, the above described protocols do not provide maintenance of time-synchronization throughout both neighbor discovery and network formation operations, while the many redundant transmissions in the protocols can cause broadcast storms through contention and collisions at the Medium Access Control (MAC) protocol layer.